1. Field of the Invention
This invention relates to a carrier being provided with molded and plated or printed circuits for functional AC, DC as well as burn-in testing of bare or non-packaged circuit chips or die, i.e., non-packaged silicon die with circuitry. The carrier comprises a base with a cover or an integrated cover-base with a film construct.
The novel carrier has metallized contacts for making electrical connection between the bare die and the perimeter of the carrier. The circuitry for electrically connecting the die and the perimeter of the carrier can be molded and plated into the base or printed on polymeric film. The base or integrated cover-base of the carrier may be thermoplastic molded to conform to any intended package for the die, such as plastic Quad Flat Package (QFP), Leadless Chip Carrier (LCC), Small Outline "J" lead or any other intended package design. The object is to adapt the carrier to the existing test equipment for burn-in stress and electrical tests for the intended package design without having to modify the hardware, such as: the burn-in sockets, the circuit boards or the automatic test handler.
2. Description of the Related Prior Art
There is an increasing demand for new electronic products which are smaller and lighter. As a result, there is an emerging demand for bare die that are completely electrical and burn-in tested. For example, smart cards are now as slim as the standard credit cards. The multichip module manufacturers design circuits stipulating several different types of chips having different functions to make a hybrid package. The smart card manufacturers and the makers of multichip hybrids require bare die instead of packaged die.
Users of bare die expect die suppliers to meet the stringent quality and integrity of packaged die. Thus, to ensure the quality, yield and reliability of bare die, semi-conductor or die suppliers are required by users to exercise the die by "burn-in" at elevated temperatures to reduce initial failure rate and to conduct final electrical testing to select the good die from the bad die.
The existing method of selecting functioning good die from bad die involves the use of a wafer probe. In wafer probing, electrical signals are sent to a test fixture containing several spring probe needles typically made of tungsten. Each probe is correspondingly aligned to each die pad and each die is individually tested on a wafer before cutting. Ideally, it would be desirable to have the testing of the uncut die on a wafer done at elevated temperatures. However, the thermal expansion of the spring probe needles of the probe tends to cause scrubbing and tearing of the bond pads on the die and cracking of its external protective coating. Therefore, burn-in testing using a wafer probe is limited in the temperature ranges that can be applied.
Some prior art approaches in mounting bare circuit chips on a module or carrier for burn-in or electric testing are described in U.S. Pat. No. 4,899,107: "Discrete Die Burn-In For Nonpackaged Die" and U.S. Pat. No. 5,123,850: "Non-Destructive Burn-In Test Socket For Integrated Circuit Die."
U.S. Pat. No. 4,899,109 discloses a reusable burnin/test fixture for discrete TAB die. The fixture comprises two parts: a die cavity plate to receive die as units under test and a probe plate where each probe is connected to electrical traces which terminate in fingers to accept a conventional card edge connector. The probes tips are metallic needles and protrude from the probe plate to contact the die pads. Thus, it suffers from the same problem as wafer probing. At high temperatures, due to thermal expansion the probe tips still cause scrubbing and tearing of the die pads, particularly when low contact resistance is maintained.
U.S. Pat. No. 5,123,850 describes a burn-in test socket for integrated circuit die. The socket comprises three parts, a metal base with a flexible film probe head, a pin grid array package attached to the probe head and a clamp to hold the device in place. The socket is suitable for testing a plurality of die, a wafer or hybrid packaged die. The flexible film probe head is formed from film coated aluminum, from which aluminum is partially removed by etching. The pads and traces are provided by electroplating. A clear elastomer is poured into the back of the film and cured. Thus, the film probe head is very complicated and is produced by a very complicated process. Moreover, the members of the socket must be aligned properly for it to function.